1. Field of the Invention
The present invention relates to a surveying instrument having an optical distance meter, and also relates to a surveying instrument having an optical distance meter and a focus detection device for detecting a focus state of a distance-measuring optical system such as a sighting telescope.
2. Description of the Related Art
When a surveyor measures the distance between two points, an electronic distance meter (EDM) designed as a surveying instrument is generally used. An electronic distance meter calculates the distance via the phase difference between a projecting light and a reflected light and via the initial phase of an internal reference light, or via the time difference between the projecting light and the reflected light.
A typical electronic distance meter is provided, behind the objective lens of a sighting telescope (distance-measuring optical system) thereof, with a light transmitting mirror positioned on the optical axis of the sighting telescope to project the measuring light toward a target (sighting object) through the center of the entrance pupil of the objective lens of the sighting telescope. The light which is reflected by the target and passed through the objective lens of the sighting telescope passes the peripheral space of the light transmitting mirror to be captured via a wavelength selection filter and a light receiving mirror.
In such an electronic distance meter, the light which is reflected by the target and passed through the objective lens of the sighting telescope is interrupted by the aforementioned light transmitting mirror by a greater amount as the target is closer to the electronic distance meter. If the light which is reflected by the target and passed through the objective lens of the sighting telescope is interrupted by the light transmitting mirror by a great amount, the light amount of the incident light upon the aforementioned light receiving mirror decreases, which deteriorates the precision in measuring the object distance or makes it impossible to perform a distance measuring operation. To prevent these problems from occurring, various methods have been proposed.
The present invention has been devised in view of the problems noted above, and accordingly, an object of the present invention is to provide a surveying instrument having an optical distance meter, wherein the aforementioned problems can be overcome in an easy manner without deteriorating the performance characteristics of the distance measuring operation of the optical distance meter when measuring the distance to a target at the maximum measurable distance.
Another object of the present invention is to provide a surveying instrument having an optical distance meter and a focus detection device for detecting a focus state of a distance-measuring optical system, wherein the aforementioned problems can be overcome in an easy manner without deteriorating the performance characteristics of the distance measuring operation of the optical distance meter when measuring the distance to a target at the maximum measurable distance.
To achieve the objects mentioned above, according to an aspect of the present invention, a surveying instrument is provided, including a distance-measuring optical system having an objective lens via which a distance from the surveying instrument to an object is measured; and an optical distance meter which includes a reflection member positioned behind the objective lens, a light-transmitting optical system for transmitting a measuring light toward the object via the reflection member and the objective lens, and a light-receiving optical system for receiving a portion of the measuring light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member. The light-receiving optical system includes a plurality of light-guiding optical systems, so that the measuring light which is reflected by the object is selectively incident on an end of one of the plurality of light-guiding optical systems in accordance with the distance from the surveying instrument to the object.
In an embodiment, a diameter of at least one light-guiding optical system of the plurality of light-guiding optical systems, to which the measuring light reflected by the object is incident on, is greater as the object distance for which at least one light-guiding optical system is used is longer.
In an embodiment, the surveying instrument further includes a light shield mask having a plurality of apertures, wherein the measuring light reflected by the object is selectively incident on the end of the one of the plurality of light-guiding optical systems via one of the plurality of apertures.
In an embodiment, diameters of the plurality of apertures are different from one another, the diameters of the plurality of light-guiding optical systems being identical to one another.
In an alternative embodiment, diameters of the plurality of apertures are different from one another, wherein the diameters of the plurality of light-guiding optical systems correspond to the diameters of the plurality of apertures of the light shield mask.
The surveying instrument can further include a moving device for moving the light shield mask so that the measuring light reflected by the object can be selectively incident on the end of the one of the plurality of light-guiding optical systems.
Preferably, the distance-measuring optical system includes a focus adjustment lens which is moved to bring the object into focus; the surveying instrument further including a lens position detection device which detects an axial position of the focus adjustment lens, the moving device moving the light shield mask in accordance with the axial position of the focus adjustment lens that is detected by the lens position detection device.
Preferably, a controller is provided, which controls the moving device to move the light shield mask in accordance with a state of the light-receiving optical system when the light-receiving optical system receives the measuring light reflected by the object.
The controller can include a mask position detector for detecting a position of the light shield mask in which an amount of the measuring light reflected by the object and received by the light-receiving optical system becomes maximum. The controller controls the moving device to move the light shield mask in accordance with the position of the light shield mask that is detected by the mask position detector.
The controller can control, for example, the moving device to move the light shield mask so that the measuring light reflected by the object is incident on an end of another one of the plurality of light-guiding optical systems in the case where an amount of the measuring light reflected by the object and received by the light-receiving optical system via the one of the plurality of light-guiding optical systems, at a predetermined amount of time, is not greater than a predetermined amount of light.
In an embodiment, the central axes of the incident end surfaces of the plurality of light-guiding optical systems are positioned on a straight line.
In an alternative embodiment, the light-receiving optical system includes a light-receiving element on which the measuring light reflected by the object is incident via the plurality of light-guiding optical systems; wherein the central axes of the exit end surfaces of the plurality of light-guiding optical systems are positioned on a circle about an axis of the light-receiving element.
In an embodiment, the light-receiving optical system includes a plurality of light-receiving elements on which the measuring light reflected by the object is incident via the plurality of light-guiding optical systems, respectively.
Preferably, each of the plurality of light-receiving elements is an optical fiber.
The distance-measuring optical system can be a sighting telescope for sighting the object.
Preferably, the reflection member is made of a parallel-plate mirror having a front surface and a rear surface which are parallel to each other. The front surface faces the objective lens and is formed as a light transmitting mirror which reflects the measuring light to be projected toward the object via the objective lens. The rear surface is formed as a light receiving mirror which reflects the measuring light reflected by the object. The measuring light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member, is reflected by the light receiving mirror to be selectively incident on the end of the one of the plurality of light-guiding optical systems in accordance with the distance from the surveying instrument to the object.
Preferably, the light shield mask has a sector shape.
The light-receiving optical system can include a wavelength selection mirror positioned between the reflection member and the focus adjustment lens.
According to another aspect of the present invention, a surveying instrument is provided, including a distance-measuring optical system having an objective lens via which a distance from the surveying instrument to an object is measured; an optical distance meter which includes a reflection member positioned behind the objective lens, a light-transmitting optical system for transmitting a measuring light via the reflection member and the objective lens, and a light-receiving optical system for receiving light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member, the light-receiving optical system including a light-guiding optical system, the measuring light which is reflected by the object being incident on an incident end surface of the light-guiding optical system, a diameter of the light-receiving optical system being determined so that the measuring light which is reflected by the object can be incident on the incident end surface of the light-guiding optical system regardless of the distance from the surveying instrument to the object; and a light shield mask having a central aperture via which a central portion of the incident end surface is exposed with respect to the reflection member, and at least one side aperture via which an off-center portion of the incident end surface is exposed with respect to the reflection member, a diameter of each the at least one side aperture being smaller than a diameter of the central aperture.
In an embodiment, at least two side apertures are provided, a diameter of each of the at least two side apertures is smaller as the each of the at least two side apertures is farther from the central aperture.
The above-mentioned at least one side aperture can be communicatively connected with the central aperture.
Preferably, each of the plurality of light-receiving elements is an optical fiber.
The distance-measuring optical system can be a sighting telescope for sighting the object.
In an embodiment, the reflection member is made of a parallel-plate mirror having front and rear surfaces parallel to each other. The front surface faces the objective lens and is formed as a light transmitting mirror which reflects the measuring light to be projected toward the object via the objective lens. The rear surface is formed as a light receiving mirror which reflects the measuring light reflected by the object. The measuring light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member, is reflected by the light receiving mirror to be incident on the incident end surface of the light-guiding optical system.
The above-described light shield mask can have a disc shape.
According to another aspect of the present invention, a surveying instrument is provided, including a distance-measuring optical system having an objective lens via which a distance from the surveying instrument to an object is measured; an optical distance meter which includes a reflection member positioned behind the objective lens, a light-transmitting optical system for transmitting a measuring light toward the object via the reflection member and the objective lens, and a light-receiving optical system for receiving light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member; and a focus detection device which detects a focus state of the distance-measuring optical system. The light-receiving optical system includes a plurality of light-guiding optical systems; a light shield mask having a plurality of apertures via which the measuring light reflected by the object is selectively incident on an end of one of the plurality of light-guiding optical systems in accordance with the distance from the surveying instrument to the object; a moving device for moving the light shield mask so that the measuring light reflected by the object can be selectively incident on the end of the one of the plurality of light-guiding optical systems; and a controller which controls the moving device to move the light shield mask so that the measuring light reflected by the object is incident on the end of the one of the plurality of light-guiding optical systems in accordance with the focus state that is detected by the focus detection device.
In an alternative to the above-described aspect of the present invention, a surveying instrument is provided, equipped with an autofocus system, including a distance-measuring optical system having an objective lens via which a distance from the surveying instrument to an object is measured; an optical distance meter which includes a reflection member positioned behind the objective lens, a light-transmitting optical system for transmitting a measuring light toward the object via the reflection member and the objective lens, and a light-receiving optical system for receiving light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member; a focus detection device which detects a focus state of the distance-measuring optical system; and an autofocus mechanism for moving a focusing lens of the distance-measuring optical system to bring the object into focus in accordance with the focus state that is detected by the focus detection device, the autofocus mechanism including a lens position detection device which detects an axial position of the focusing lens. The light-receiving optical system includes a plurality of light-guiding optical systems; a light shield mask having a plurality of apertures via which the measuring light reflected by the object is selectively incident on an end of one of the plurality of light-guiding optical systems in accordance with the distance from the surveying instrument to the object; a moving device for moving the light shield mask so that the measuring light reflected by the object can be selectively incident on the end of the one of the plurality of light-guiding optical systems; and a controller which controls the moving device to move the light shield mask so that the measuring light reflected by the object is incident on the end of the one of the plurality of light-guiding optical systems in accordance with the axial position of the focusing lens that is detected by the lens position detection device.
In an embodiment, diameters of the plurality of apertures are different from one another, and the diameters of the plurality of light-guiding optical systems are identical to one another.
In an alternative embodiment, the diameters of the plurality of apertures can be different from one another so that the diameters of the plurality of light-guiding optical systems correspond to the diameters of the plurality of apertures of the light shield mask.
In an embodiment, the distance-measuring optical system includes a sighting telescope for sighting the object. The focus detection device includes a phase-difference detection type focus detection device which detects the focus state of the sighting telescope from a correlation between a pair of images respectively formed by two light bundles which are respectively passed through two different pupil areas on the objective lens. Elements of the optical distance meter are positioned so as not to interfere with the two different pupil areas.
In an embodiment, the central axes of the incident end surfaces of the plurality of light-guiding optical systems are positioned on a straight line.
In an embodiment, the light-receiving optical system includes a light-receiving element on which the measuring light reflected by the object is incident via the plurality of light-guiding optical systems. The central axes of the exit end surfaces of the plurality of light-guiding optical systems are positioned on a circle about an axis of the light-receiving element.
In an embodiment, the light-receiving optical system includes a plurality of light-receiving elements on which the measuring light reflected by the object is incident via the plurality of light-guiding optical systems, respectively.
Preferably, each of the plurality of light-receiving elements is an optical fiber.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2000-175221 (filed on Jun. 12, 2000) which is expressly incorporated herein by reference in its entirety.